Caffeine Dosage

Ask the Coach

I don't drink coffee in the morning, but like my caffeine. I take a 200-milligram caffeine supplement prior to my runs ...

Illustration by Jeremy Collins

I don't drink coffee in the morning, but like my caffeine. I take a 200-milligram caffeine supplement prior to my runs and was wondering how long it is effective. On a 25- to 30-mile run, when should I take more supplement?

—Scott Hamilton, Corona, CA

For many runners, enjoying their pre-run coffee is a ritual, and we have all felt the ergogenic benefits of caffeine. It goes to work on the central nervous system and can decrease tiredness, improve mood, sharpen alertness and increase reaction time. The effects of caffeine peak about an hour after ingestion, whether it's from coffee, tea or a pill.

The half life, or the time it takes for the body to eliminate one half of the caffeine consumed, varies widely between individuals. Says Registered Dietician Adrienne Aldous, "Most studies report the half life is between three and six hours."

For a four- to six-hour run, you could get by on one dose. This should be enough to boost your performance, and avoid the side effects of over-caffeinating. Aldous continues, "Due to the body's rapid tolerance to caffeine, it best aids the performance of athletes who do not habitually use it. "

Your goal should be to ingest caffeine as an infrequent performance booster, and not to rely on it daily to achieve your weekly mileage. Relying on any stimulant for your runs is not prudent. Eventually you have to pay that energy back.